This patent deals generally with material coating, and more specifically with an apparatus and a method for coating limited areas of a moving web with particulate matter.
One type of product in the flooring industry requires the application of particle such as different colored vinyl particles on sheet material to create a pattern. This is accomplished by first applying a pattern of adhesive to the sheet material, and then covering the adhesive with the particles which are to be attached to the sheet. This application of particles has typically involved covering the entire sheet with particles to a uniform depth, and then removing all the loose particles, i.e. those which have not adhered to the adhesive pattern. In many circumstances this can entail supplying five times the amount of particles that are actually needed, and, of course, removing 80% of the particles from the sheet material before subsequent processing.
The removal of such a large quantity of particles is a major task. It usually involves blowing high pressure, high volume air against the sheet to dislodge the loose particles and simultaneously using a large vacuum pickup to remove the particles from the sheet. These processes are both performed on a continuous, fast moving, wide width sheet, which requires air supply and vacuum pickup fixtures which span the entire width of the sheet and can handle very large volumes.
Moreover, because of the large excess used, the loose particles removed from the sheet must be recycled. This recycling can then be the source of contamination of the particles by dirt, moisture, adhesive, and other foreign matter, and such contamination can cause separation of the components in the particles. The particles used are frequently actually a mix of different colors and textures, and any contamination or separation can cause inconsistent and unacceptable final product.
It would be very advantageous to have a means for adhering particles to a moving sheet which did not involve the application of a quantity of particles which greatly exceeded the amount actually remaining on the sheet. It would be particularly beneficial if any excess of particles applied to the sheet were so small that there would be no need to recycle the excess or that contamination of the applied particles from the small amount of recycled material would be minimized.